TPA3116D2: PBTL mode direct driving 70/100 V transformer installed Hi Z speakers without transformers

Dear Derek,

Thank you very much for your prompt response, very appreciated.

In my circuit the amp  works only PBTL mode , and mono so these big 680 UF Caps were introduced to the output. I also put the 680 uF capacitors due the reason which they will act  like a HPF and pass over crossover over point of 60 Hz , I can replace them with 1UF/100 Volt version with your suggestion.

Do you have any example circuits and or more information on how to drive the circuit with inductors and where to introduce them for the drive of High İmpedance speakers?

If i dont also go through the EMI test, would it be possible without inductors?

Thank you

Dear Derek , Thank you for your reply. 

Do you mean to remove the standart 10 uH /5.8 A rated inductor on each of the  output of OUTPR and OUTPL and drive the tranformer of the speaker directly through 1 uF capacitor?

If İ  need to enter the EMI test , how can i handle the EMI with this HiZ transformer of the speakers? As you mentioned below, where shoudl i introduce the İnductors apart from the 10UH inductors?

I really appreciate your support on this. 

Thank you.

Regards,

Ferhan 

Hi Ferhan,

Do you have the spec of transformer of the speaker? 

How about the load impedance and inductance value?

Regards,

Derek

Dear Derek , Thank you very much for your response.

The typical 70V transformer with different wattage shows the below measurements, 

3 Watt -1.8 H inductance @1 Khz with 2Kohm impedance @1 Khz measured with RLC meter. RMS multimeter shows 100 Ohm impedance.

7.5 Watt-  700 mH inductance @1 khz with 1550 ohm impedance@1 kHZ measured with LRC meter . RMS multimeter shows 15 ohm impedance.

15 Watt - 350 mH İnductance @ 1 Khz with 800 ohm impedance @1 Khz measured with LRC meter . RMS multimeter shows 8.8 ohm impedance.

30 Watt - 180 mH Inductance@ 1 Khz with 400 ohm impedance @1 Khz measured with LRC meter. RMS multimeter shows 4.6 ohm impedance.

The  idea is ,  we dont want to drive big loads of 70V speakers. Only 4 or upto 6 pcs of 7.5 watt models or less. Which one of the above rating is more suitable for our amplifier which is in PBTL mode without using a Step up transformer with our 3116D2 amplifier.

Thank you for your support. 

Dear Derek , One of the speaker was 15 ohm and 7.5 Watt. We want to  add 4 pcs to 6 pcs in parallel , that makes about 3.75 ohm with 4 speakers and 30 watts in total.

is there a guideline that will help us  designing snubber circuit values according to the power on the output? 

To understand it clear, from the evaluation board below;

I already have the L1 and L2 10 uH inductors that is connected to the OUTPR and OUTPL , Are we talking about these inductor or adding another one on the output before the speaker connection?

We have  0.68 uF capacitors C21 to the ground as adviced on the TPA 3116d2 evaluation board like your C1 . Also the R15 and C25 were added which the values will be corrected according to the new load snubber circuit update ( 3.75 ohm , 30 Watt). We also need to add  a 4K resistor tp GND?

Thank you in advance.

regards,

Dear Derek.

I hope that you are doing well, 

In the original attached below 3116D2 EVM , you can see the jumper (shorting of outputs) on the  Left and Right Side of the Amplifier with Blue tags. Our design is now operating both BTL and PBTL according to our selection now. so my question is i have 2 pcs of 10 uH inductors on OUTPR and OUTNR  for Right side and the same for Left side respectively, and also the snubber capacitors in each line  now,  i am shorting the outputs with  relay contacts  on the PBTL mode as in the picture. Is this type of operation allowed in PBTL Mode having 2 inductors and all the capacitors still connected for BTL mode?

Thank you